Press die, drawing method, and pressed product

ABSTRACT

A press die for molding an edge wall at a peripheral edge of a workpiece includes a die convexly formed along a shape of one surface of the edge wall, a punch formed with a concave portion along the other surface of the edge wall, and a stripper for holding the workpiece with the die therebetween, wherein a clearance between the die and the punch is in a range of not less than 70% and not more than 95% of a thickness of the workpiece before forming.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a press die, a drawing method using the press die, and a pressed product molded by the drawing method.

2. Description of the Related Art

In a pressed product in which a peripheral edge wall is molded at a peripheral edge, the edge wall may be molded by drawing.

Drawing is a forming method in which for example, when a peripheral edge wall is molded at a peripheral edge of a workpiece, the peripheral edge of the workpiece is bent while a pressing force is applied to the edge wall portion.

When the peripheral edge of the workpiece is bent, an excess part of the material (redundant part) may occur, causing wrinkles; however, drawing the redundant part while pressing it allows the occurrence of the wrinkles to be prevented.

In such a drawing method, the peripheral edge wall of a uniform thickness is molded by applying the pressing force with a punch to the workpiece placed on a die to thereby bend the workpiece while maintaining a clearance between the die and the punch comparable to (or slightly thicker than) a thickness of the workpiece.

Also, as another press forming method for molding the peripheral edge wall, there exists a method in which a pressing force is applied to a workpiece, which is a plate, using a die formed with a concave portion, and a punch with a shape capable of being inserted into the concave portion, as shown in Japanese published unexamined patent application No. 2005-186113. This press forming method is intended to mold a pressed product with a vertical wall (peripheral edge wall) by molding a concave portion on the plate and then cutting a peripheral edge of the concave portion of the plate.

At this time, a clearance between the die and the punch, which is set in a range of not less than 30% and not more than 90% of a thickness of the workpiece, is molded to be smaller than the thickness. Thus the workpiece is stretched and thereby the peripheral edge wall portion is molded while being ironed in a starvation state of its thickness being thinner than the clearance.

However, regarding a press die used in the conventional drawing, it is difficult to uniformly make the clearance between the punch and the die throughout, thus causing uniformity of the pressing force during press forming on a metal plate to be difficult. For this reason, a problem has existed that a flat portion of a pressed product after forming is not flattened and uniformly warped.

There has also been a problem that nonuniform warpage occurs in the flat portion when an outer periphery of the workpiece is partially notched or the workpiece having a shape asymmetric with respect to a point or a line is formed.

On the other hand, in the press forming method described in the Japanese published unexamined patent application No. 2005-186113, the vertical wall portion is stretched and thereby always in the starvation state during the press forming, so that a member in a flat portion continuous with the vertical wall is under a tensile condition. The tension under this condition does not uniformly occur throughout the entire flat portion, and therefore there has existed a problem that nonuniform warpage occurs in the flat portion. Particularly, in a workpiece having a smaller thickness (for example, 0.5 mm or less), deformation is more likely to occur in relation to a difference in strain, so that it has been difficult to control warpage. Furthermore, in a pressed product with a larger ratio of its external dimension to its thickness, occurring strain is easily amplified and controlling warpage tends to be more difficult.

The present invention has been made to solve the above-described problems and therefore an objective of the present invention is to propose a press die enabling the occurrence of warpage in the flat portion inside the peripheral edge wall to be reduced, a drawing method for using the press die, and a pressed product molded by the drawing method when the wall portion (peripheral edge wall) is molded at an outer peripheral edge by drawing.

SUMMARY OF THE INVENTION

In order to solve the above-described problems, a first aspect of the present invention is a press die for molding a peripheral edge wall at a peripheral edge of a workpiece, comprising a die convexly formed along a shape of one surface of the edge wall, a punch formed with a concave portion along the other surface of the edge wall, and a stripper for holding the workpiece with the die therebetween, and being characterized in that a clearance between the die and the punch is in a range of not less than 70% and not more than 95% of a thickness of the workpiece before forming.

Such press die allows the peripheral edge wall to be molded while the material (peripheral edge of the workpiece) is compressed because the clearance between the die and the punch is in the range of not less than 70% and not more than 95% of the thickness of the workpiece before forming. This ensures the peripheral edge wall to be pressed and bent along the peripheral edge of the die from its base, so that the peripheral edge wall is molded in a desired shape. Also, the peripheral edge wall is plastic-deformed at its base, and thereby the occurrence of warpage in a flat portion continuous with the edge wall is suppressed. In addition, in order to suppress the warpage in the flat portion, it is more effective if the clearance between the die and the punch is set in a range of not less than 80% and not more than 95% of the thickness of the workpiece. Note that if the clearance between the die and the punch is less than 70% of the thickness of the workpiece before forming, a defect such as a crack is more likely to occur on the peripheral edge wall, whereas if the clearance is more than 95% of the thickness of the workpiece before forming, a defect such as any of larger warpage and larger deformation in the flat portion is more likely to occur.

A second aspect of the present invention is a drawing method for bending a peripheral edge of a workpiece held between a die and a stripper while a pressing force is applied to the peripheral edge of the workpiece through a punch to be thereby drawn, and thus a clearance between the die and the punch is configured to be in a range of not less than 70% and not more than 95% of a thickness of the workpiece before forming.

Regarding a pressed product molded to have a peripheral edge wall, this drawing method allows warpage in a flat portion continuous with the edge wall to be reduced compared with a conventional method, and the pressed product to be molded with good flatness because the clearance between the die and the punch is set in the range of not less than 70% and not more than 95% of the thickness of the workpiece before forming. Furthermore, if the clearance between the die and the punch is set in a range of not less than 80% and not more than 95% of the thickness of the workpiece before forming, the warpage in the flat portion can be more effectively reduced. Note that if the clearance between the die and the punch is less than 70% of the thickness of the workpiece before forming, a defect such as a crack is more likely to occur on the peripheral edge wall, whereas if the clearance is more than 95% of the thickness of the workpiece before forming, a defect such as any of larger warpage and larger deformation in the flat portion is more likely to occur.

A third aspect of the present invention is a pressed product in which drawing is applied to a peripheral edge of a workpiece to thereby mold a peripheral edge wall, and is characterized in that a thickness of the edge wall is in a range of not less than 72% and not more than 97% of a thickness of the workpiece before forming, preferably in a range of not less than 82% and not more than 97%.

In such a pressed product, the peripheral edge wall is molded with high quality and a flat portion is also molded with high quality in flatness. That is, if the thickness of the edge wall is less than 72% of the thickness of the workpiece before forming, a defect such as a crack is more likely to occur on the edge wall, whereas if the thickness is more than 97% of the thickness of the workpiece before forming, a defect such as any of larger warpage and larger deformation in the flat portion is more likely to occur; however, the pressed product prevents such a defect.

Furthermore, a fourth aspect of the present invention is the pressed product according to the third aspect and is characterized in that a maximum width from a center to an edge is in a range of not less than 25 times and not more than 700 times of the thickness of the workpiece before forming.

Such a pressed product preferably allows any of warpage and deformation in a flat portion to be reduced and is thereby preferably molded with high quality if the thickness of the peripheral edge wall is molded in the range of not less than 72% and not more than 97%, preferably in the range of not less than 82% and not more than 97%. That is, if the maximum width from the center to edge of the pressed product is less than 25 times of the thickness of the workpiece before forming, stiffness due to the thickness and a size (width of the pressed product) is higher, and a defect such as any of warpage and deformation in the flat portion is less likely to occur even in the case of the thickness of the peripheral edge wall molded by general drawing. Also, if the maximum width from the center to edge of the pressed product is more than 700 times of the thickness of the workpiece before forming, a defect such as any of warpage and deformation in the flat portion occurs even if the thickness of the peripheral edge wall is molded in the range of not less than 72% and not more than 97%, preferably in the range of not less than 82% and not more than 97%.

Furthermore, a fifth aspect of the present invention is the pressed product according to the third or fourth aspect and is characterized in that a height of the peripheral edge wall is in a range of not less than 3 times and not more than 25 times of the thickness of the workpiece before forming.

Such a pressed product preferably allows the peripheral edge wall to be molded in a desired shape. That is, if the height of the peripheral edge wall is less than 3 times of the thickness of the workpiece before forming, the material cannot be sufficiently pressed or ironed during drawing, and therefore a desired shape cannot be obtained due to a larger springback; however, in the pressed product, the height is set to 3 times or more, so that molding in the desired shape is possible. Also, if the height of the peripheral edge wall is more than 25 times of the thickness of the workpiece before forming, problems such as slant of the edge wall as well as warpage in a flat portion become obvious; however, in the pressed product, such problems are avoided because the height is set to 25 times or less.

Still furthermore, a sixth aspect of the present invention is the pressed product according to any one of the third to fifth aspects and is characterized in that the thickness of the workpiece before forming is 0.5 mm or less, preferably 0.25 mm or less.

The press die and the drawing method according to the present invention enable warpage occurred in the flat portion continuous with the inside of the peripheral edge wall to be reduced when the wall portion (peripheral edge wall) is molded at the outer peripheral edge by drawing. Also, the pressed product according to the present invention has small warpage and good flatness, so that it can preferably be used as a member of a precision component and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional view illustrating a press die according to an embodiment of the present invention; FIG. 1B is an enlarged cross-sectional view illustrating a part of the press die shown in FIG. 1A.

FIGS. 2A and 2B are drawings illustrating a pressed product according to the embodiment; FIG. 2A is a perspective view; and FIG. 2B is an enlarged cross-sectional view.

FIGS. 3A, 3B, and 3C are cross-sectional views illustrating respective forming steps of a drawing method according to the embodiment.

FIGS. 4A and 4B are contour drawings illustrating a state of warpage of a pressed product in a demonstration experiment; FIG. 4A shows a case of a conventional drawing method; and FIG. 4B shows a case according to the embodiment.

FIG. 5A is a schematic drawing illustrating a measurement method of warpage; FIG. 5B is an explanatory drawing illustrating a direction of warpage.

BEST MODE FOR CARRYING OUT THE INVENTION

A best mode of the present invention will be described in detail, referring to drawings; the drawings are schematic ones and are not drawn according to an actual size. In addition, in the embodiment, as a pressed product will be described a component of a cartridge for housing a magnetic medium, more particularly, a case of molding a shutter member of the cartridge.

As shown in FIG. 1A, a press die 1 according to an embodiment of the present invention comprises a die 2 convexly formed along a shape of one surface of a peripheral edge wall 11 molded in a metal plate 10 that is a workpiece, a punch 4 concavely formed along a shape of the other surface of the edge wall 11, and a stripper 5 for holding the workpiece with the die 2 therebetween.

In the embodiment, as the metal plate 10, a plate having a thickness t of 0.25 mm or less is used. Also, in the embodiment, drawing is applied to the metal plate 10 to thereby mold a pressed product 15 with the peripheral edge wall 11 molded at its peripheral edge as shown in FIG. 2A. In a flat portion 12 continuous with the edge wall 11, an occurrence of warpage due to the drawing is reduced as well as a direction of the occurrence of the warpage is controlled by using the press die 1, and thus predetermined quality is ensured. In addition, a symbol 14 in the drawing represents a boss molded by applying burring processing to the metal plate 10.

As shown in FIG. 1A, the die 2 is protrudingly fixed in a state where it protrudes from the bottom surface of a concave portion 3 a formed on a die plate 3. In the press die 1 according to the embodiment, the die 2 is configured to be changeable, and depending on a designed shape of the pressed product 15, the die 2 shaped in a desired shape is placed.

The die 2 is shaped depending on a shape of the peripheral edge wall 11 of the designed pressed product 15 (see FIG. 2). In addition, the die 2 according to the embodiment is formed into a columnary shape of a substantially circular shape in a plan view. Also, at a peripheral edge of a surface of the die 2 on a stripper 5 side, a pair of convex portions 2 a is formed in a position opposite to each other. Furthermore, a substantially circular concave portion 2 b is formed on a substantially central part of the die 2, and is configured to prevent the boss 14 molded in advance on the workpiece from being deformed during drawing. In addition, a material constituting the die 2 is not limited, but may be appropriately selected and used from a well-known material having enough strength, which is not deformed by press-forming the metal plate 10. The concave portion 2 b of the die 2 is formed as required, but may not necessarily be formed. Also, the shape of the die 2 is not limited to the circular shape in the plan view and may be appropriately formed depending on a designed shape of the pressed product 15, such as any one of a rectangular shape, an oval shape, and another shape including a polygonal shape.

Regarding the convex portions 2 a formed on the die 2, their shapes are not limited if the convex portions 2 a and the stripper 5 can securely hold the metal plate 10 not to be misaligned during drawing. In addition, in the embodiment, each of the convex portions 2 a is formed so that its width w is in a range of not less than 100% and not more than 400% of the thickness t of the metal plate 10, preferably in a range of not less than 150% and not more than 300%, and its height h is in a range of not less than 5% and not more than 20% of the thickness t of the metal plate 10 (see FIG. 1B).

As shown in FIG. 1A, the punch 4 is a steel member having a concave portion 4 a and exhibiting an upside-down shape of a substantially depressed shape in its cross-sectional view, and is shaped so that the die 2 can be inserted into the concave portion 4 a. In the embodiment, a clearance s between a peripheral edge of the die 2 and an inner wall surface of the concave portion 4 a of the punch 4 is configured to be in a range of not less than 70% and not more than 95% of the thickness t of the metal plate 10, preferably in a range of not less than 80% and not more than 95% (see FIG. 1B).

In addition, the shape of the punch 4 is not limited and may be appropriately configured, depending on the shape of the die 2 and the shape of the peripheral edge wall of the designed pressed product 15.

Also, the embodiment is configured such that the punch 4 is brought down from above the metal plate 10 to thereby apply drawing to the metal plate 10; however, it should be appreciated that the embodiment may be configured such that the punch 4 is brought up from below, and the direction of the movement of the punch 4 is not limited.

As shown in FIG. 1A, the stripper 5 is like a plate for holding the metal plate 10 with the die 2, abutting with the metal plate 10 from a face opposite to an abutting face of the die 2 with the metal plate 10. The stripper 5 is placed in the concave portion 4 a of the punch 4, and fixed to the punch 4 via elastic members 5 a such as springs. This enables the punch 4 to be brought down while the stripper 5 presses down the metal plate 10 from its top surface.

In addition, it should be appreciated that the configuration of the stripper 5 is not limited if the stripper 5 can hold the metal plate 10 with the die 2 to thereby securely fix it.

With reference to FIGS. 3A to 3C, a drawing method according to the embodiment is now described.

As shown in FIG. 2, the embodiment describes a case where the peripheral edge wall 11 is molded at the peripheral edge of a pressed product 15. In addition, the shape of the peripheral edge wall 11 is not limited to a circular shape and may be appropriately molded in any shape depending on an application of the pressed product 15.

The drawing method according to the embodiment is comprised of a placing process of placing the metal plate 10 on the die 2, a fixing process of bringing the stripper 5 into touch with the top surface of the metal plate 10 placed on the top surface of the die 2 to thereby fix the metal plate 10, and a drawing process of pressing the punch 4 into the peripheral edge of the fixed metal plate 10 to thereby mold the peripheral edge wall 11.

<Placing Process>

As shown in FIG. 3A, the placing process is a process of placing the metal plate 10, where the boss 14 is molded, on the surface of the die 2 fixed to the top surface of a die plate 3 (concave portion 3 a) in a protruding state. At this time, the metal plate 10 is placed in a state where the boss 14 is inserted into the concave portion 2 b formed on the center of the die 2.

In the placing process, the stripper 5 is held at an elevated position along with the punch 4, and a space is formed between the stripper 5 and the die 2, which enables the metal plate 10 to move.

<Fixing Process>

As shown in FIG. 3B, the fixing process is a process of pressing the stripper 5 against the top surface (surface on the opposite side of the die 2 side) of the metal plate 10 placed on the top surface of the die 2 and holding the metal plate 10 between the stripper 5 and the die 2 to thereby fix it. At this time, the convex portions 2 a formed opposite to each other at the peripheral edge of the die 2 bite into the metal plate 10 to thereby securely fix it.

The fixation of the metal plate 10 is carried out by bringing the stripper 5 down. As the stripper 5 is brought down, it is brought into close contact with the metal plate 10 without any space. In the embodiment, as the stripper 5 is brought down, the punch 4 is also brought down, and a lower end of the punch 4 abuts with the top surface of the metal plate 10. In addition, in the fixing process, it should be appreciated that only the stripper 5 may be brought down without bringing the punch 4 down.

<Drawing Process>

As shown in FIG. 3C, the drawing process is a process of pressing the punch 4 into a groove formed between the peripheral edge of the die 2 to which the metal plate 10 is fixed in the fixing process and the die plate 3 to thereby apply drawing to the peripheral edge of the metal plate 10. The punch 4 molds the peripheral edge wall 11 by downwardly pressing and bending the peripheral edge portion of the metal plate 10 protruding from the peripheral edge of the die 2. At this time, a clearance s between the die 2 and the punch 4 is formed to be less than the thickness t of the metal plate 10 (not less than 70% and not more than 95%), so that drawing is applied while the peripheral edge of the metal plate 10 is pressed and bent along the peripheral edge of the die 2, and while the inner wall surface of the concave portion 4 a of the punch 4 and the outer peripheral surface of the die 2 iron the peripheral edge wall 11 portion. Accordingly, concave portions 13 are molded on the pressed product 15 at positions corresponding to the convex portions 2 a of the die 2.

As described above, the pressed product 15 according to the embodiment has the concave portions 13 molded at the substantially point symmetric positions with respect to the center of gravity of a shape projected in the pressing direction. As shown in FIG. 2B, the concave portion 13 of the pressed product 15 is molded in a part of the flat portion continuous with the base of the peripheral edge wall 11 so that its width w1 is in a range of not less than 100% and not more than 400% of the thickness t of the metal plate 10, preferably in a range of not less than 150% and not more than 300%, and its height h1 is in a range of not less than 5% and not more than 20% of the thickness t of the metal plate 10.

The peripheral edge wall 11 of the pressed product 15 according to the embodiment is molded so that a thickness t2 of the edge wall 11 is in a range of not less than 72% and not more than 97% of the thickness t of the metal plate 10 before forming, preferably in a range of not less than 82% and not more than 97%, and a height h2 of the edge wall 11 is in a range of not less than 3 times and not more than 25 times of the thickness t of the metal plate 10 before forming, preferably not less than 4 times and not more than 18 times. In addition, the maximum length x from the center to peripheral edge (peripheral edge wall 11) of the pressed product 15 is molded to be in a range of not less than 25 times and not more than 700 times of the thickness t of the metal plate 10 before forming, preferably not less than 50 times and not more than 550 times.

The press die 1 and the drawing method for using the press die 1 according to the embodiment allow warpage occurring in the flat portion 12 continuous with the peripheral edge wall 11 of the molded pressed product 15 to be reduced as described above, so that the high-quality pressed product 15 can be molded.

Also, using the die 2 provided with the convex portions 2 a in the positions opposite to each other enables the direction of the occurrence of warpage to be controlled so as to correspond to the direction orthogonal to the convex portions 2 a.

Furthermore, the press die 1 is configured such that the clearance s between the die 2 and the punch 4 is slightly less than the thickness t of the metal plate 10, so that regarding the molding of the peripheral edge wall 11 after forming, the thickness t2 and height h2 of the edge wall 11 can be molded to be constant respectively because the edge wall 11 is formed while being ironed.

Still furthermore, the press die 1 securely fixes the metal plate 10 because the convex portions 2 a are formed at the peripheral edge of the top surface of the die 2, so that even when a pressing force is applied by the punch 4, the metal plate 10 never moves. This prevents the metal plate 10 from moving outside the die 2 along with lowering of the punch 4, and thus the height h2 of the peripheral edge wall 11 is constantly molded.

The preferred embodiment of the present invention has been described as above; however, the present invention is not limited to the above-described embodiment, but the design may be changed appropriately without departing from the spirit and scope of the present invention.

For example, in the above-described embodiment, the thickness t of the metal plate 10 is set to 0.25 mm or less; however, a thickness of a workpiece capable of being formed by the press die 1 and the drawing method according to the present invention is not limited and may be appropriately set to, for example, 0.5 mm or less.

Also, a material for the workpiece is not limited and, for example, any one of stainless steel SUS (Steel Use Stainless) 304-SP (Steel Plate), aluminum (Al), and stainless steel SUS304-CSP (Cold rolled stainless steel for Springs) may be used to obtain a similar effect.

Furthermore, it should be appreciated that the press die of the present invention may be used as an independent die or a part of a progressive die.

Still furthermore, the above-described embodiment describes a case where a part of a cartridge for housing a magnetic medium, more particularly, a shutter member of the cartridge is molded; however, it should be appreciated that any of the application and shape of the pressed product molded by the press die and drawing method of the present invention is not limited.

EXAMPLE

A result of a demonstration experiment regarding an enhancement in quality of the pressed product 15 molded by the press die 1 and the drawing method according to the present invention will be described.

In this demonstration experiment, drawing was performed under a condition that the clearance s between the die 2 and the punch 4 was varied, and warpage in the flat portion 12 of pressed products was measured to thereby demonstrate the quality enhancement effect (reduction of an amount of the warpage in the flat portion 12) based on the drawing method of using the press die 1 according to the present invention.

In this demonstration experiment, the metal plate 10 (stainless steel SUS 304-SP) having a thickness of 0.15 mm was used. The state of warpage in the flat portion 12 was measured for and compared with each of two cases where the clearances s between the die 2 and the punch 4 were set to 100% (s=0.15 mm) of the thickness t of the metal plate 10 and 90% (s=0.135 mm) of the thickness t of the metal plate 10.

FIGS. 4A and 4B show contour drawings illustrating states of warpage of pressed products after drawing based on the demonstration experiment; FIG. 4A shows the case where the clearance s between the die 2 and the punch 4 was set to the same value as the thickness t of the metal plate 10 based on a conventional drawing method; and FIG. 4B is the case where the clearance s was set to 90% of the thickness t of the metal plate 10 based on the drawing method according to the embodiment.

In addition, the warpage of the pressed products was measured in the following manner. As shown in FIG. 5A, coordinates of three points (a, b, c) on the base of the boss 14 were measured using a laser displacement meter L to thereby form a virtual plane A. Then, displacements in the flat portion 12 were measured while the laser displacement meter L was moved in a longitudinal, transverse, and diagonal direction of the metal plate 10 on which the boss was molded, to thereby measure the warpage in the flat portion 12 with respect to the virtual plane A formed by the coordinates of the three points a, b, and c. Note that regarding “+” and “−”, the warpage to the opposite side of the protruding portion of the boss 14 is expressed as “+”, and that to the boss 14 side as “−”, as shown in FIG. 5B.

As shown in FIG. 4A, contour lines CL are drawn densely for a pressed product 15′ based on the conventional drawing method, and it turns out that the flat portion 12 of the pressed product 15′ is significantly warped (maximum value of warpage is 437 μm). Also, there exist a part where the contour lines CL are dense (part with larger warpage) and a part where they are sparse (part with smaller warpage), and it turns out that flatness of the flat portion 12 is nonuniform.

On the other hand, in the pressed product 15 according to the embodiment, as shown in FIG. 4B, the contour lines CL are sparse compared with those of the conventional pressed product 15′, exhibiting that the occurrence of the warpage is reduced (maximum value of the warpage is 164 μm).

From the above result, it has been demonstrated that setting the clearance s between the die 2 and the punch 4 less than the thickness t of the metal plate 10 (not less than 70% and not more than 95%, preferably not less than 80% and not more than 95%) allows the occurrence of the warpage of the flat portion 12 of the pressed product 15 after drawing to be reduced. 

1. A press die for forming an edge wall at a peripheral edge of a workpiece, the press die comprising: a die formed convexly along a shape of one face of the edge wall; a punch formed concavely along a shape of the other face of the edge wall; and a stripper configured to sandwich the workpiece together with the die, wherein a clearance between the die and the punch is in a range of not less than 70% and not more than 95% of a thickness of the workpiece before forming.
 2. The press die according to claim 1, wherein a convex portion width of the die is in a range of not less than 100% and not more than 400% of the thickness of the workpiece before forming and a height of the die is formed in a range of not less than 5% and not more than 20% of the thickness of the workpiece before forming.
 3. The press die according to claim 2, wherein the die comprises the convex portions at opposed positions.
 4. A drawing method comprising the step of: bending a peripheral edge of a workpiece sandwiched by a die and a stripper while the peripheral edge being drawn by applying a pressing force through a punch, wherein a clearance between the die and the punch is in a range of not less than 70% and not more than 95% of a thickness of the workpiece before forming.
 5. A pressed product comprising: an edge wall formed by dispensing drawing at a peripheral edge of a workpiece, wherein a thickness of the peripheral edge is in a range of not less than 72% and not more than 97% of a thickness of the workpiece before forming.
 6. A pressed product according to claim 5, wherein a maximum width from a center to an edge is in a range of not less than 25 times and not more than 700 times of the thickness of the workpiece before forming.
 7. The pressed product according to claim 5, wherein a height of the edge wall is in a range of not less than three times and not more than 25 times of the thickness of the workpiece before forming.
 8. The pressed product according to claim 6, wherein a height of the edge wall is in a range of not less than three times and not more than 25 times of the thickness of the workpiece before forming.
 9. The pressed product according to claim 5, wherein the thickness of the workpiece before forming is not more than 0.5 mm.
 10. The pressed product according to claim 6, wherein the thickness of the workpiece before forming is not more than 0.5 mm.
 11. The pressed product according to claim 7, wherein the thickness of the workpiece before forming is not more than 0.5 mm.
 12. The pressed product according to claim 8, wherein the thickness of the workpiece before forming is not more than 0.5 mm.
 13. The pressed product according to claim 5, wherein the workpiece is any one of stainless steel SUS (Special Use Stainless) 304-SP (Steel Plate), aluminum, and stainless steel SUS 304-CSP (Cold rolled stainless steel for Springs).
 14. The pressed product according to claim 6, wherein the workpiece is any one of stainless steel SUS304-SP, aluminum, and stainless steel SUS 304-CSP.
 15. The pressed product according to claim 7, wherein the workpiece is any one of stainless steel SUS304-SP, aluminum, and stainless steel SUS 304-CSP.
 16. The pressed product according to claim 8, wherein the workpiece is any one of stainless steel SUS304-SP, aluminum, and stainless steel SUS 304-CSP.
 17. The pressed product according to claim 9, wherein the workpiece is any one of stainless steel SUS304-SP, aluminum, and stainless steel SUS 304-CSP.
 18. The pressed product according to claim 10, wherein the workpiece is any one of stainless steel SUS304-SP, aluminum, and stainless steel SUS 304-CSP.
 19. The pressed product according to claim 11, wherein the workpiece is any one of stainless steel SUS304-SP, aluminum, and stainless steel SUS 304-CSP. 